Q: does it hurt the engine to drive with a defective oxygen sensor? on 2002 Nissan Pathfinder

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The check engine light came on and when I took it in to the dealer, he quoted me $500 to replace it. Will it hurt the engine to drive with the defective sensor?
(1) Answer
Oxygen sensors that do not work typically suggest to the engine's computer that it needs to supply more fuel to the engine to make it run properly. This excessive fuel amount then has to go somewhere - and often it goes out the exhaust. Your most likely failure in the short term is the catalytic converter, where unburned fuel will cause the temperature of the converter to rise to unsafe levels. This will eventually damage the precious metals inside the converter and possibly even restrict it. Catalytic converters are expensive to replace. Even more than an oxygen sensor.

You can also cause unnecessary wear in the engine from excessive fuel, and additionally -- you will have a reduction of fuel economy as well, since you are wasting unnecessary fuel.

In this economy, often times we have to prioritize, and I totally am with you on that. Replacing your oxygen sensor is a pretty necessary repair for the operation and longevity of your Pathfinder.